Lithium copper composite electrode and its preparation method and application

Abstract

The present invention discloses a lithium-copper composite electrode and a preparation method and application thereof. The preparation method comprises: 1) forming a lithium-philic layer on the surface of a copper-containing electrode; 2) forming a metallic lithium layer on the surface of the lithium-philic layer, thereby forming the lithium-copper composite electrode. The preparation method of the lithium-copper composite negative electrode provided by the present invention has simple process, high controllability and low cost; the method adopts different composite methods for different lithium-philic metals. Due to the presence of the copper substrate, on the one hand, the current can be evenly distributed in the negative electrode during the charging and discharging process, which can effectively reduce uneven lithium deposition and inhibit the growth of lithium dendrites. On the other hand, it provides the negative electrode with more excellent mechanical properties, thermal stability and chemical stability.

Description

Technical Field

[0001] The present invention particularly relates to a lithium-copper composite electrode and a preparation method and application thereof, belonging to the technical field of batteries. Background Art

[0002] In recent years, due to the rapid development of the power battery market, the energy density requirements for secondary batteries have become increasingly higher. The existing graphite-based lithium metal anode can no longer meet the requirements of power batteries. Therefore, the research and development of high-capacity anode materials has become a hot topic in the industry. Metal lithium has a low density (0.59 g / cm 3 ), small reduction potential (-3.04V), high theoretical specific capacity (3860mAh / g) and other advantages are considered to be ideal negative electrode materials. For example, existing high-energy-density lithium secondary batteries, lithium-sulfur batteries, and lithium-air batteries all use lithium metal as negative electrodes. However, its disadvantages are also very obvious. During the charge and discharge process, uneven lithium deposition leads to the formation of lithium dendrites. The growth of lithium dendrites may pierce the diaphragm and cause battery short circuit or even explosion. During the charge and discharge process, lithium metal will have an obvious "volume effect", which will cause the volume of the battery to expand, posing a hidden danger to the safety performance of metal lithium batteries. At the same time, the soft, light, and very active properties of lithium metal itself increase the difficulty of its large-scale production and processing. Therefore, the research and development of high-safety, long-cycle, and easy-to-process lithium metal negative electrodes is imminent. Summary of the invention

[0003] The main purpose of the present invention is to provide a lithium-copper composite electrode and a preparation method and application thereof, thereby overcoming the deficiencies in the prior art.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0005] An embodiment of the present invention provides a method for preparing a lithium-copper composite electrode, which comprises:

[0006] 1) Forming a lithium-philic layer on the surface of the copper-containing electrode;

[0007] 2) forming a metallic lithium layer on the surface of the lithium-philic layer, thereby forming the lithium-copper composite electrode.

[0008] The embodiment of the present invention also provides a lithium-copper composite electrode prepared by the preparation method.

[0009] The embodiment of the present invention further provides a lithium-copper composite electrode, which includes a copper substrate, a lithium-philic layer formed on the surface of the copper substrate, and a metal lithium layer formed on the surface of the lithium-philic layer.

[0010] The embodiment of the present invention also provides the use of the lithium-copper composite electrode in preparing a secondary battery.

[0011] The embodiment of the present invention further provides a secondary battery, wherein the negative electrode of the secondary battery is the lithium-copper composite electrode.

[0012] Compared with the prior art, the advantages of the present invention include:

[0013] 1) The copper substrate in the lithium-copper composite negative electrode provided by the present invention can effectively increase the mechanical properties, thermal stability and chemical stability of the composite electrode, improve the processability of metallic lithium, and reduce production costs;

[0014] 2) The lithium-copper composite negative electrode provided by the present invention is more conducive to the uniform transfer of charge, effectively improves the uniformity of current distribution, avoids the phenomenon of lithium dendrites due to excessive local current, and improves the cycle performance of the battery;

[0015] 3) The lithium-copper composite negative electrode provided by the present invention uses a copper mesh as a copper substrate. The porous structure of the lithium-copper composite negative electrode provides more deposition space for the excess lithium generated during the cycle, reduces the volume expansion during the cycle, and improves the safety performance of the battery;

[0016] 4) The lithium-copper composite negative electrode provided by the present invention enables the composite electrode to effectively improve the higher performance, electrochemical performance and safety performance of lithium metal negative electrode secondary batteries;

[0017] 5) The method for preparing the lithium-copper composite negative electrode provided by the present invention has a simple process, high controllability and low cost; the method adopts different composite methods for different lithium-philic metals. Due to the presence of the copper substrate, on the one hand, the current can be evenly distributed in the negative electrode during the charge and discharge process, which can effectively reduce uneven lithium deposition and inhibit the growth of lithium dendrites. On the other hand, it provides the negative electrode with more excellent mechanical properties, thermal stability and chemical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of a method for preparing a lithium-copper composite negative electrode in a typical embodiment of the present invention;

[0019] Figure 2 is a cycle curve diagram of a secondary battery prepared using the modified lithium-copper composite negative electrode obtained in Example 1 of the present invention;

[0020] Figure 3 is a cycle curve diagram of a secondary battery prepared using the modified lithium-copper composite negative electrode obtained in Example 2 of the present invention;

[0021] Figure 4 is a cycle curve diagram of a secondary battery prepared using the modified lithium-copper composite negative electrode obtained in Example 3 of the present invention;

[0022] Figure 5is a cycle curve diagram of a secondary battery prepared using the modified lithium-copper composite negative electrode obtained in Example 4 of the present invention;

[0023] Figure 6 is a cycle curve diagram of a secondary battery prepared using the modified lithium-copper composite negative electrode obtained in Example 5 of the present invention;

[0024] Figure 7 It is a cycle curve diagram of a secondary battery prepared with the modified lithium-copper composite negative electrode obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0025] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0026] An embodiment of the present invention provides a method for preparing a lithium-copper composite electrode, which comprises:

[0027] 1) Forming a lithium-philic layer on the surface of the copper-containing electrode;

[0028] 2) forming a metallic lithium layer on the surface of the lithium-philic layer, thereby forming the lithium-copper composite electrode.

[0029] Furthermore, the material of the lithium-philic layer includes a lithium-philic compound.

[0030] Furthermore, the lithium-philic compound comprises a lithium-philic active metal compound M x O y and lithium-philic inactive metal compounds N x O y Any one of .

[0031] Furthermore, the M includes any one of Zn and Sn, and the N includes any one of Ni, Mn, and Co, but is not limited thereto.

[0032] In some more specific embodiments, step 1) comprises: heating the electrode comprising Cu and M in an oxygen atmosphere at 200-500° C. for 1-5 h, thereby forming the lithium-philic layer on the surface of the copper-containing electrode, wherein the lithium-philic layer is a lithium-philic active metal compound M x O y , the electrode piece containing Cu and M is an alloy formed by Cu and M.

[0033] In some more specific embodiments, step 1) specifically includes: placing the copper-containing electrode in a chemical immersion plating reaction solution and reacting at 100-200° C. for 0.5-16 hours, heating the copper-containing electrode after the reaction treatment in a protective atmosphere at 200-400° C. for 1-5 hours, and then forming the lithium-philic layer on the surface of the copper-containing electrode, wherein the lithium-philic layer is a lithium-philic inactive metal compound N x O y , the copper-containing pole piece includes a pure copper pole piece or a copper-containing alloy.

[0034] In some more specific embodiments, the step 1) further comprises: Preferably, the protective atmosphere comprises an inert atmosphere.

[0035] In some specific embodiments, the lithium-philic layer is NiO 2 or NiO, forming the NiO 2 or NiO using a reaction solution containing 0.05-0.2 mol / L NiCl 2 、0.2~0.8mol / L CO(NH 2 ) 2 A mixed solution;

[0036] In some specific embodiments, the lithium-philic layer is MnO 2 , forming the MnO 2 The reaction solution used includes 0.01-0.1 mol / L MnSO 4 , 0.01~0.1mol / L KMnO 4 , a mixed solution of 20 to 60 mL of deionized water.

[0037] In some specific embodiments, the lithium-philic layer is CoO, and the reaction solution used to form the CoO includes 0.1-0.5 mol / L Co(NO 3 ) 2 6H 2 O and 0.05~0.2mol / L CO(NH 2 ) 2 of mixed solution.

[0038] In some more specific embodiments, the step 2) comprises: placing molten metallic lithium on the surface of the lithium-philic layer, and then cooling for 30 to 60 minutes to form the metallic lithium layer.

[0039] In some more specific embodiments, the preparation method further comprises: cleaning the copper-containing electrode before step 1).

[0040] Preferably, the cleaning process comprises: cleaning the copper-containing electrode with a cleaning agent, and then drying it at 50-100° C. under vacuum conditions.

[0041] Preferably, the cleaning agent includes any one of acetone, ethanol and distilled water or a combination of two or more thereof, but is not limited thereto.

[0042] Furthermore, the copper-containing electrode is a sheet-like or mesh-like structure.

[0043] The embodiment of the present invention also provides a lithium-copper composite electrode prepared by the preparation method.

[0044] The embodiment of the present invention further provides a lithium-copper composite electrode, which includes a copper substrate, a lithium-philic layer formed on the surface of the copper substrate, and a metal lithium layer formed on the surface of the lithium-philic layer.

[0045] Furthermore, the material of the lithium-philic layer includes a lithium-philic compound.

[0046] Furthermore, the lithium-philic compound comprises a lithium-philic active metal compound M x O y and lithium-philic inactive metal compounds N x O y , the M includes any one of Zn and Sn, and the N includes any one of Ni, Mn, and Co, but is not limited thereto.

[0047] Furthermore, the material of the copper substrate includes pure copper or an alloy containing copper.

[0048] Furthermore, the copper-containing alloy includes an alloy mainly composed of Cu and M or N.

[0049] Furthermore, the copper substrate is a sheet or mesh structure.

[0050] Furthermore, the copper substrate has a thickness of 10 to 50 μm.

[0051] Furthermore, the mesh size of the copper substrate of the mesh structure is 5 to 500 meshes.

[0052] Furthermore, the thickness of the lithium-philic layer is 20-50 μm.

[0053] Furthermore, the thickness of the metal lithium layer is 200-800 μm.

[0054] Furthermore, the mass of the lithium-copper composite electrode is 300-600 mg.

[0055] The embodiment of the present invention also provides the use of the lithium-copper composite electrode in preparing a secondary battery.

[0056] The embodiment of the present invention further provides a secondary battery, wherein the negative electrode of the secondary battery is the lithium-copper composite electrode.

[0057] Furthermore, the secondary battery includes a lithium-sulfur battery, a lithium-air battery or a lithium-ion battery.

[0058] The technical solution, its implementation process and principle will be further explained as follows.

[0059] Figure 1 The schematic diagram of the process of preparing a novel lithium copper composite negative electrode of the present invention is as follows. It should be noted that, due to the chemical properties of the lithium metal negative electrode being very active, it can react with O in the air. 2 , H 2 O、CO 2 Therefore, the preparation of lithium copper metal negative electrode sheets and the assembly of secondary batteries are carried out in a dry glove box filled with argon, where the water content is ≤0.5ppm and the oxygen content is ≤0.5ppm.

[0060] Specifically, a lithium-copper composite electrode includes a copper substrate, a lithium-philic layer formed on the surface of the copper substrate, and a metallic lithium layer formed on the surface of the lithium-philic layer.

[0061] The copper substrate may be made of pure copper or a copper-containing alloy, and its structure may be copper foil (i.e., the aforementioned sheet structure) or copper mesh (i.e., the aforementioned mesh structure); the lithium-philic layer may be a lithium-philic compound or a metal element; the lithium-philic compound includes a lithium-philic active metal compound M x O y and lithium-philic inactive metal compounds N x O y , the M includes any one of Zn and Sn, and the N includes any one of Ni, Mn and Co.

[0062] The modified lithium-copper composite electrode obtained by the present invention has stable cycle performance, can effectively inhibit the generation of lithium metal negative electrode dendrites, and can be widely used in new high-energy-density electrochemical energy storage devices, such as lithium-ion batteries, lithium-air batteries, lithium-sulfur batteries, etc.

[0063] The present invention provides a novel method for preparing a lithium-copper composite negative electrode with simple process, high controllability and low cost. The method adopts different composite methods for different lithium-philic metals. Due to the presence of the copper substrate, on the one hand, the current can be evenly distributed in the negative electrode during the charge and discharge process, which can effectively reduce uneven lithium deposition and inhibit the growth of lithium dendrites. On the other hand, it provides the negative electrode with more excellent mechanical properties, thermal stability and chemical stability.

[0064] Specifically, a method for preparing a lithium-copper composite electrode comprises the following steps:

[0065] 1) Use acetone, ethanol and distilled water to clean the copper-containing electrode in turn. After three cycles of cleaning, place the electrode in a vacuum drying oven and dry it at 50-100°C for 24 hours before cutting;

[0066] 2) Forming a lithium-philic layer mainly composed of a lithium-philic compound or a metal element on the surface of the copper-containing electrode by a physical method or a chemical method, wherein the lithium-philic layer completely covers the copper-containing electrode;

[0067] 3) pouring molten metallic lithium uniformly on the copper-containing electrode with the lithium-philic layer on the surface, and cooling for 30 to 60 minutes to form a metallic lithium layer on the surface of the lithium-philic layer, thereby forming the lithium-copper composite electrode;

[0068] 4) First, the lithium-copper composite electrode sheet is rolled using a roller with a clean and flat surface to make its surface flat, and then a polishing rod (500-1000 mesh) is used to transversely polish the surface of the lithium-copper composite electrode sheet until the surface of the lithium-copper composite electrode presents a shiny silver-white metallic luster, thereby obtaining the final lithium-copper composite electrode.

[0069] Specifically, when the copper-containing electrode is a mesh structure, that is, when a copper mesh is used as the copper-containing electrode for preparing a composite electrode, the porous structure (or mesh structure) of the composite electrode provides more deposition space for the excess lithium generated during the cycle process (here, it refers to the use of a lithium-copper composite electrode as an anode to assemble a battery for charge and discharge cycles), effectively reducing the generation of dendrites and volume expansion. At the same time, the lithium-copper metal composite electrode has a larger specific surface area than the lithium sheet, which is beneficial to the transfer of charge and reduces the local current density.

[0070] Specifically, the lithium-philic compound includes a lithium-philic active metal compound M x O y and lithium-philic inactive metal compounds N x O y , the M includes any one of Zn and Sn, and the N includes any one of Ni, Mn and Co.

[0071] In some more specific embodiments, since the lithium-philic active metal can react with oxygen before copper and can reduce copper oxide, the lithium-philic active metal compound M can be formed by physical methods. x O y , the reaction principle is as follows:

[0072] 2xM+yO 2 →2M x O y ;

[0073] xM+yCuO→M x O y +yCu;

[0074] Accordingly, the physical method is used to prepare the lithium-philic active metal compound M x O y The corresponding copper-containing pole piece is an alloy containing Cu and M (M is Zn, Sn, etc.), such as commercial brass (Cu / Zn alloy, the mass fraction of Zn is 20-50%) and commercial bronze (Cu / Sn alloy, the mass fraction of Sn is 5-10%).

[0075] Specifically, the lithium-philic active metal compound M is formed by a physical method. x The process of O includes placing the cleaned brass or bronze electrode in a tube furnace, heating it to 200-500°C in an oxygen atmosphere, reacting for 1-5 hours, and then forming a copper-containing electrode with a surface-coated lithium-philic active metal oxide layer.

[0076] Specifically, brass (Cu / Zn alloy) provides a Zn source for the in-situ growth of ZnO, and bronze (Cu / Sn alloy) provides a SnO 2 The in-situ growth of Sn can provide Sn source, which not only reduces the preparation materials and the preparation cost, but also simplifies the preparation process and improves the controllability of the preparation process; and, because the stacking fault energy of brass, bronze, etc. is low, it can ensure that the lithium-philic active metal (Zn, Sn, etc.) atoms are uniformly diffused to the copper surface at high temperature (part or all of M in the copper alloy can be diffused to the surface, as long as it is sufficient to form the lithium-philic active metal compound), thereby forming a uniform lithium-philic active metal compound (ZnO, SnO 2 ) layer, avoiding the lithium-philic active metal compounds (ZnO, SnO 2 ) layer is uneven, so the metal lithium layer formed by subsequent casting is more uniform, and the lithium / lithium-philic active metal compound (Cu / M x O y , M=Zn, Sn, etc.) / copper composite electrodes have better electrochemical and mechanical properties; in addition, the physical method process only involves high-temperature annealing. Compared with the chemical method, it has fewer controlled variables, lower equipment requirements, and a simpler preparation process. Therefore, this method is easier to scale up production and has greater commercial application potential.

[0077] In other more specific implementation schemes, the lithium-philic non-active metal N (Ni, Mn, Co, etc.) is chemically inactive and difficult to reduce the CuO produced in the high-temperature process. Therefore, it can only be prepared by chemical methods, which increases the selection range of lithium-philic metals and provides more preparation options for the preparation of lithium-copper composite electrodes; wherein the chemical method includes chemical immersion plating.

[0078] Specifically, the lithium-philic active metal compound N is formed by a physical method. x O y The process includes: placing the cleaned copper-containing electrode piece in a 100 mL polytetrafluoroethylene-lined stainless steel autoclave, adding 60 to 80 mL of reaction solution thereto, and reacting at 100 to 200° C. for 0.5 to 16 hours, washing the reacted copper-containing electrode piece with ethanol and deionized water alternately for several times, and then drying it, and finally treating the dried copper-containing electrode piece in a tube furnace filled with argon atmosphere at 200 to 400° C. for 1 to 5 hours, thereby forming the lithium-philic inactive metal compound N x O y layer; wherein the copper-containing electrode may be pure copper or a copper-containing alloy, such as an alloy containing Cu and N.

[0079] In some more specific embodiments, different reaction solutions are used for different lithium-philic inactive metal compounds, for example:

[0080] When the lithium-philic inactive metal compound is NiO, the reaction solution used includes 0.05-0.2 mol / L NiCl 2 、0.2~0.8mol / L CO(NH 2 ) 2 The chemical reaction principle is as follows:

[0081]

[0082] NiCl 2 +2NH 3 ·H 2 O→Ni(OH) 2 ↓+2NH 4 Cl;

[0083] When the lithium-philic inactive metal compound is MnO 2 When the reaction solution used includes 0.01-0.1 mol / L KMnO 4 , a mixed solution of 0.1-0.5 mL concentrated HCl (mass fraction 37%) and 60 mL deionized water; the chemical reaction principle is as follows:

[0084] 3MnSO 4 +2KMnO 4 +2H 2 O→5MnO 2 ↓+K 2 SO 4 +2H 2 SO 4 ;

[0085] When the lithium-philic inactive metal compound is CoO, the reaction solution used includes 0.1-0.5 mol / L Co(NO 3 ) 2 6H 2 O, 0.05~0.2mol / LC 6 H 12 N 4 The chemical reaction principle of the mixed solution is as follows:

[0086]

[0087] Co(NO 3 ) 2 +2NH 3 ·H 2 O→Co(OH) 2 ↓+2NH 4 (NO 3 ) 2 ;

[0088] Based on the above chemical reaction principle, it can be seen that for the production of certain materials such as MnO 2 For lithium-philic inactive metal oxides such as nickel oxide and cobalt oxide, after the copper-containing electrode is reacted in the reaction solution, Ni(OH) is generated on the surface of the copper-containing electrode. 2 、Co(OH) 2 , it is also necessary to treat the copper-containing electrode after the reaction in a tube furnace filled with argon atmosphere at 200-400°C for 1-5h to obtain NiO and CoO respectively.

[0089] In some more specific embodiments, the step 3) includes: in a glove box filled with argon, placing the weighed metallic lithium on a high-temperature heating table, heating at 100-500°C for 2-5 hours, until molten metallic lithium is formed, and the molten metallic lithium is in the shape of a silvery white sphere; then placing the molten metallic lithium in the center of the lithium-philic layer, and making the metallic lithium evenly cover the lithium-philic layer, and then cooling for 30-60 minutes to form a metallic lithium layer. Compared with the existing physical extrusion method, this method (molten lithium casting) can better bond the lithium layer with the lithium-philic layer and the copper-containing pole piece. At the same time, when a 3D copper mesh is used as a copper-containing pole piece, the molten lithium can be fully diffused to the surface of the copper mesh to avoid incomplete coverage of the metallic lithium layer.

[0090] Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

[0091] Example 1

[0092] 1) In a glove box, place a commercially available brass mesh (mesh size 30 mesh / cm 2 ) Use long-blade scissors to cut to obtain a rectangular brass electrode with a size of 6×8.5 cm, use acetone, ethanol, and distilled water to clean the brass electrode in turn, and cycle the cleaning for 3 times, then place the brass electrode in a 200°C vacuum drying oven for drying for 24 hours; then place the cleaned brass electrode in a tube furnace, heat to 200-500°C in an air atmosphere, and react for 3 hours to form a copper-containing electrode with a zinc oxide layer coated on the surface;

[0093] 2) In a glove box filled with argon, 300 mg of metallic lithium was placed on a high-temperature heating table and heated at 300° C. for 2 h until it was molten, and the molten metallic lithium was in the shape of a silvery white sphere; the molten metallic lithium was placed in the center of the treated zinc oxide layer so that the metallic lithium covered the surface of the zinc oxide layer, and cooled for 60 min to form a metallic lithium layer, thereby obtaining a lithium-copper composite electrode with a metallic lithium layer coated on the surface;

[0094] 3) firstly rolling the composite electrode sheet with a clean and flat roller to make its surface flat, and then using a polishing rod (500-1000 mesh) to perform transverse polishing on the surface of the lithium-copper composite electrode sheet until the surface of the lithium-copper composite electrode sheet presents a shiny silver-white metallic luster, thus obtaining a lithium-copper composite electrode sheet;

[0095] 4) The prepared lithium-copper composite electrode is coated with a diaphragm and assembled to form a secondary battery, wherein the secondary battery is a lithium-sulfur secondary soft-pack battery, the positive electrode comprises sulfur, a conductive agent, and a binder, the negative electrode is a lithium-copper composite negative electrode, and the electrolyte is LiTFSI / DME-DOL (0.1-5% LiNO 3 As an additive), the assembled battery is placed on a battery testing device for testing, and the secondary battery cycle curve is obtained as follows Figure 2 shown.

[0096] Example 2

[0097] This embodiment is basically the same as the above-mentioned embodiment 1; the difference is that the copper-containing electrode used in embodiment 2 is a commercial bronze mesh (mesh number is 30 mesh / cm 2 ), the other specific preparation process is the same as that of Example 1, the assembled secondary battery is the same as that of Example 1, and the secondary battery cycle curve is as follows Figure 3 shown.

[0098] Example 3

[0099] 1) In a glove box, commercially purchased pure copper foil (thickness 30 μm) was cut with long-blade scissors to obtain a rectangular copper electrode with a size of 6×8.5 cm. The copper electrode was cleaned with acetone, ethanol, and distilled water in turn, and the cleaning cycle was repeated 3 times. After that, the copper electrode was placed in a vacuum drying oven at 80°C and dried for 24 hours;

[0100] 2) 0.75g NiCl 2 The solid and 0.42 g of urea are dissolved in 60 mL of deionized water, and magnetically stirred at a speed of 100 to 500 rpm for 10 to 40 min to form a clear solution, i.e., the aforementioned reaction solution;

[0101] 3) placing the cleaned copper pole piece in a 100 mL polytetrafluoroethylene-lined stainless steel autoclave, adding 60 mL of the prepared reaction solution, and reacting at 100-200° C. for 0.5-16 h; washing the reacted copper pole piece with distilled water for 3 times, and drying it at 120° C. for 4 h, then placing the copper pole piece in a tube furnace, reacting it at 350° C. for 4 h in an argon atmosphere, to form a copper pole piece with a surface coated with nickel oxide (NiO);

[0102] 4) In a glove box filled with argon, 300 mg of metallic lithium was placed on a high-temperature heating table and heated at 300° C. for 2 h until it was molten, and the molten metallic lithium was in the shape of a silvery white sphere; the molten metallic lithium was placed in the center of the nickel oxide layer so that the metallic lithium covered the surface of the nickel oxide layer, and cooled for 60 min to form a metallic lithium layer, thereby obtaining a lithium-copper composite electrode with a nickel oxide layer coated on the surface;

[0103] 5) firstly roll the lithium-copper composite electrode sheet with a clean and flat roller to make its surface flat, and then use a polishing rod (500-1000 mesh) to polish the surface of the lithium-copper composite electrode sheet laterally until the surface of the lithium-copper composite electrode sheet presents a shiny silver-white metallic luster, thus obtaining a lithium-copper composite negative electrode sheet;

[0104] 6) A lithium copper composite electrode coated with a diaphragm is used as a lithium negative electrode to be assembled into a secondary battery, wherein the secondary battery is a lithium sulfur secondary soft pack battery, wherein the positive electrode includes sulfur, a conductive agent, and a binder, and the electrolyte is LiTFSI / DME-DOL (0.1-5% LiNO 3 As an additive), the assembled battery is placed on a battery testing device for testing, and the secondary battery cycle curve is obtained as follows Figure 4 shown.

[0105] Example 4

[0106] 1) In a glove box, commercially purchased pure copper foil (30 μm thick) was cut with long-blade scissors to obtain a rectangular copper electrode with a size of 6×8.5 cm. The copper electrode was cleaned with acetone, ethanol, and distilled water in turn, and the cleaning cycle was repeated 3 times. The copper electrode was then placed in a vacuum drying oven at 80°C and dried for 24 h.

[0107] 2) 2.535 g MnSO 4 The solid was dissolved in 50 mL of deionized water, and 1.58 g of KMnO 4 Mix with 60 mL of deionized water to make MnSO 4 The solution was slowly added to the KMnO 4 The solution is magnetically stirred at a speed of 100 to 500 rpm for 10 to 40 min, and the resulting clear solution is used as a reaction solution;

[0108] 3) Place the cleaned copper electrode in a 100 mL polytetrafluoroethylene-lined stainless steel autoclave, add 60 mL of the prepared reaction solution, and react at 140 ° C for 0.5 h. Wash the reacted copper electrode with distilled water for 3 times and dry it at 120 ° C for 4 h to form a surface-coated manganese oxide (MnO 2 ) of copper electrode;

[0109] 4) In a glove box filled with argon, 300 mg of metallic lithium was placed on a high temperature heating table and heated at 300° C. for 2 h to form molten metallic lithium, which was in the shape of silvery white spheres. The molten metallic lithium was placed at the center of the treated manganese oxide layer so that the metallic lithium covered the surface of the manganese oxide layer. After cooling for 60 min, a metallic lithium layer was formed to obtain a composite electrode covered with a metallic lithium layer on the surface;

[0110] 5) firstly roll the composite electrode sheet with a clean and flat roller to make its surface flat, and then use a polishing rod (500-1000 mesh) to transversely polish the surface of the lithium-copper composite electrode sheet until the surface of the lithium-copper composite electrode sheet presents a shiny silver-white metallic luster, thus obtaining a lithium-copper composite electrode sheet;

[0111] 6) A lithium copper composite electrode coated with a diaphragm is used as a lithium negative electrode to be assembled into a secondary battery, wherein the secondary battery is a lithium sulfur secondary soft pack battery, wherein the positive electrode includes sulfur, a conductive agent, and a binder, and the electrolyte is LiTFSI / DME-DOL (0.1-5% LiNO 3 As an additive), the assembled battery is placed on a battery testing device for testing, and the secondary battery cycle curve is obtained as follows Figure 5 shown.

[0112] Example 5

[0113] 1) In a glove box, commercially purchased pure copper foil (thickness 30 μm) was cut with long-blade scissors to obtain a rectangular copper electrode with a size of 6×8.5 cm. The copper electrode was cleaned with acetone, ethanol, and distilled water in turn. After three cycles of cleaning, the copper electrode was placed in a vacuum drying oven at 80°C and dried for 24 hours.

[0114] 2) 1.75 g Co(NO 3 ) 2 The solid and 0.36 g of urea solid are dissolved in 60 mL of deionized water, and magnetically stirred at a speed of 100 to 500 rpm for 10 to 40 min, and the formed clear solution is used as the reaction solution;

[0115] 3) The cleaned copper electrode piece is placed in a 100 mL polytetrafluoroethylene-lined stainless steel autoclave, 60 mL of the prepared reaction solution is added, and the reaction is carried out at 100-200° C. for 0.5-16 h. The reacted copper electrode piece is washed with distilled water for 3 times, dried at 120° C. for 4 h, and then placed in a tube furnace, heated at 250° C. for 2.5 h in an argon atmosphere to form a copper electrode piece with a surface coated with cobalt oxide (CoO);

[0116] 4) In a glove box filled with argon, 300 mg of metallic lithium was placed on a high-temperature heating table and heated at 300° C. for 2 h to form molten metallic lithium, which was in the shape of a silvery white sphere. The molten metallic lithium was placed at the center of the treated cobalt oxide layer so that the metallic lithium covered the surface of the cobalt oxide layer. After cooling for 60 min, a metallic lithium layer was formed to obtain a composite electrode covered with a metallic lithium layer on the surface;

[0117] 5) firstly roll the composite electrode sheet with a clean and flat roller to make its surface flat, and then use a polishing rod (500-1000 mesh) to transversely polish the surface of the lithium-copper composite electrode sheet until the surface of the lithium-copper composite electrode sheet presents a shiny silver-white metallic luster, thus obtaining a lithium-copper composite electrode sheet;

[0118] 6) A lithium copper composite electrode coated with a diaphragm is used as a lithium negative electrode to be assembled into a secondary battery, wherein the secondary battery is a lithium sulfur secondary soft pack battery, wherein the positive electrode includes sulfur, a conductive agent, and a binder, and the electrolyte is LiTFSI / DME-DOL (0.1-5% LiNO 3 As an additive), the assembled battery is placed on a battery testing device for testing, and the secondary battery cycle curve is obtained as follows Figure 6 shown.

[0119] Comparative Example 1

[0120] 1) In a glove box, a commercially available lithium ribbon (thickness 100 μm) was cut with long-bladed scissors to obtain a rectangular lithium metal electrode with a size of 6×8.5 cm;

[0121] 2) First, the lithium sheet is rolled using a roller with a clean and flat surface to make its surface flat, and then a polishing rod (500-1000 mesh) is used to transversely polish the surface of the lithium electrode sheet until the surface of the lithium electrode sheet presents a shiny silver-white metallic luster, thus obtaining a lithium electrode sheet;

[0122] 3) The prepared lithium electrode sheet is coated with a separator to form a lithium negative electrode and assembled into a secondary battery. The battery system is a lithium-sulfur secondary soft-pack battery, the positive electrode is sulfur, a conductive agent, and a binder, the negative electrode is a lithium metal negative electrode, and the electrolyte is LiTFSI / DME-DOL (0.1-5% LiNO 3 As an additive), the assembled battery is placed on a battery testing device for testing, and the secondary battery cycle curve is obtained as follows Figure 7 shown.

[0123] contrast Figures 2 to 7 The cycling curves shown in the figure show that the new lithium-copper composite electrode exhibits better electrochemical performance, among which the copper / zinc oxide / lithium negative electrode ( Figure 2 ) decayed to 80% of the initial capacity at 65 cycles, and the copper / tin oxide / lithium negative electrode ( Figure 3 ) decayed to 80% of the initial capacity at 47 cycles, the copper / nickel oxide / lithium negative electrode ( Figure 4 ) decayed to 80% of the initial capacity at 54 cycles, and the copper / manganese oxide / lithium negative electrode ( Figure 5 ) decayed to 80% of the initial capacity at 51 cycles, and the copper / cobalt oxide / lithium negative electrode ( Figure 6 ) decayed to 80% of the initial capacity at 47 cycles, both of which are better than pure lithium negative electrode ( Figure 7 ) decays to 80% of the initial capacity after 11 cycles, which shows that this method has a significant effect on improving the cycle performance of the battery cell; at the same time, the operation process of the present invention is simple and controllable, and has a broad application prospect.

[0124] It should be noted that the bronze, brass, pure copper, copper-containing alloys, etc. used in the embodiments of the present invention can be purchased commercially, and the copper content of pure copper is greater than 99.5%.

[0125] The present invention provides a novel lithium-copper composite negative electrode and a preparation method thereof. The copper substrate in the formed lithium-copper composite negative electrode can effectively increase the mechanical properties, thermal stability and chemical stability of the composite electrode, improve the processability of metallic lithium, and reduce production costs. In addition, the composite electrode is more conducive to uniform charge transfer, effectively improves the uniformity of current distribution, avoids the phenomenon of lithium dendrites due to excessive local current, and improves the cycle performance of the battery. In addition, when the copper mesh is used as the copper substrate, the porous structure of the lithium-copper composite negative electrode provides more deposition space for excess lithium generated during the cycle, reduces volume expansion during the cycle, and improves the safety performance of the battery. As a result, the composite electrode can effectively improve the higher performance, electrochemical performance and safety performance of lithium metal negative electrode secondary batteries.

[0126] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a lithium-copper composite electrode, characterized in that include: 1) Forming a lithium-philic layer on the surface of the copper-containing electrode: The electrode containing Cu and M is heated in an oxygen atmosphere at 200-500° C. for 1-5 hours to form the lithium-philic layer on the surface of the copper-containing electrode. The lithium-philic layer is a lithium-philic active metal compound M. x O y , the electrode piece containing Cu and M is an alloy formed by Cu and M, and the M is selected from any one of Zn and Sn; or, the copper-containing electrode piece is placed in a chemical immersion reaction solution and reacted at 100-200°C for 0.5-16 h, and the copper-containing electrode piece after the reaction is heated in a protective atmosphere at 200-400°C for 1-5 h, thereby forming the lithium-philic layer on the surface of the copper-containing electrode piece, and the lithium-philic layer is a lithium-philic inactive metal compound N x O y , wherein N is selected from any one of Ni, Mn and Co; 2) forming a metallic lithium layer on the surface of the lithium-philic layer: placing molten metallic lithium on the surface of the lithium-philic layer, and then cooling for 30 to 60 minutes to form the metallic lithium layer, and then forming the lithium-copper composite electrode.

2. The preparation method according to claim 1, characterized in that: The protective atmosphere is an inert atmosphere.

3. The preparation method according to claim 1, characterized in that: The lithium-philic layer is NiO, and the reaction solution used to form the NiO includes a mixed solution containing 0.05~0.2 mol / L NiCl2 and 0.2~0.8 mol / L CO(NH2)2; and / or, the lithium-philic layer is MnO2, and the reaction solution used to form the MnO2 includes a mixed solution containing 0.01~0.1 mol / L MnSO4 and 0.01~0.1 mol / L KMnO4; and / or, the lithium-philic layer is CoO, and the reaction solution used to form the CoO includes a mixed solution containing 0.1~0.5 mol / L Co(NO3)2·6H2O and 0.05~0.2 mol / L CO(NH2)2.

4. The preparation method according to claim 1, characterized in that: The preparation method further comprises: cleaning the copper-containing electrode piece before step 1); and / or the copper-containing electrode piece is a sheet-like or mesh-like structure.

5. The preparation method according to claim 4, characterized in that The cleaning process includes: cleaning the copper-containing electrode with a cleaning agent, and then drying it at 50-100° C. under vacuum conditions.

6. The preparation method according to claim 5, characterized in that: The cleaning agent includes any one of acetone, ethanol and distilled water or a combination of two or more thereof.

7. A lithium-copper composite electrode prepared by the preparation method according to any one of claims 1 to 6, characterized in that It includes a copper substrate, a lithium-philic layer formed on the surface of the copper substrate, and a metallic lithium layer formed on the surface of the lithium-philic layer. The copper substrate is made of pure copper or a copper-containing alloy. The copper-containing alloy is an alloy mainly composed of Cu and M or N. The copper substrate is a sheet or mesh structure.

8. The lithium-copper composite electrode according to claim 7, characterized in that The thickness of the copper substrate is 10-50 μm; and / or the mesh size of the copper substrate with a mesh structure is 5-500 mesh; and / or the thickness of the lithium-philic layer is 20-50 μm; and / or the thickness of the metal lithium layer is 200-800 μm; and / or the mass of the lithium-copper composite electrode is 300-600 mg.

9. Use of the lithium-copper composite electrode as claimed in claim 7 or 8 in the preparation of a secondary battery.

10. A secondary battery, characterized in that: The negative electrode of the secondary battery is the lithium-copper composite electrode described in any one of claims 7-8; the secondary battery is a lithium-sulfur battery, a lithium-air battery or a lithium-ion battery.

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